DAQmxReadCounterF64

NI-DAQmx C Functions

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DAQmxReadCounterF64

int32 DAQmxReadCounterF64 (TaskHandle taskHandle, int32 numSampsPerChan, float64 timeout, float64 readArray[], uInt32 arraySizeInSamps, int32 *sampsPerChanRead, bool32 *reserved);

Purpose

Reads multiple floating-point samples from a counter task. Use this function when counter samples are scaled to a floating-point value, such as for frequency and period measurements.

Parameters

Input
Name Type Description
taskHandle TaskHandle The task to read samples from.
numSampsPerChan int32 The number of samples, per channel, to read. The default value of -1 (DAQmx_Val_Auto) reads all available samples. If readArray does not contain enough space, this function returns as many samples as fit in readArray.
NI-DAQmx determines how many samples to read based on whether the task acquires samples continuously or acquires a finite number of samples.
If the task acquires samples continuously and you set this parameter to -1, this function reads all the samples currently available in the buffer.
If the task acquires a finite number of samples and you set this parameter to -1, the function waits for the task to acquire all requested samples, then reads those samples. If you set the Read All Available Samples property to TRUE, the function reads the samples currently available in the buffer and does not wait for the task to acquire all requested samples.
timeout float64 The amount of time, in seconds, to wait for the function to read the sample(s). The default value is 10.0 seconds. To specify an infinite wait, pass -1 (DAQmx_Val_WaitInfinitely). This function returns an error if the timeout elapses.
A value of 0 indicates to try once to read the requested samples. If all the requested samples are read, the function is successful. Otherwise, the function returns a timeout error and returns the samples that were actually read.
arraySizeInSamps uInt32 The size of the array, in samples, into which samples are read.
reserved bool32 * Reserved for future use. Pass NULL to this parameter.
Output
Name Type Description
readArray float64 [] The array to read samples into.
sampsPerChanRead int32 * The actual number of samples read from each channel.

Return Value

Name Type Description
status int32 The error code returned by the function in the event of an error or warning. A value of 0 indicates success. A positive value indicates a warning. A negative value indicates an error.
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